This is a fine example of Plot.
Kakuzu was destroying Kakashi despite the latter having access to a MS Sharingan, and support from a Sensor as well as Choji's expansion jutsu.
He also managed to fight and survive against Hashirama without Jiongu (Earth Grudge Fear). He also has bar none the most combat experience in the Narutoverse (at 92 years of Age and having lived in the same relative time period as Hashirama, Tobirama, Izuna, and Madara).
Even then, his death or loss was completely plot contributed...
Kakuzu decided to switch to long range mode. Which grants him the octopus appearance as well as his Katon-Fuuton combination attack. Despite having both the ranged Jiongu tendrils as well as a devastating ranged attack, he literally charges Naruto (engaging someone in CQB while in Long Range Mode)! With his experience... this is completely irrational.
I won't even get into how in the world Naruto can switch places with Clones despite the fact there was no noticeable smoke screen let alone a swapping of positions.
Additionally, Kakuzu has been noted to be an Earth Style user by Shikaku which means for some ungodly known reason, Kakuzu stopped using Doton: Domu which can arguably tank the Rasenshuriken (and before you claim it outclasses, Kakuzu has been seen using his B-Rank jutsu to match the force of S-Rank jutsu... just observe Raiton: Gian vs Raiton: Raikiri).
Needless to say... it was all literally the desire to end the arc, and show off a Jutsu. Even then it failed to kill Kakuzu...